Generally, batteries are used to supply power to portable devices such as personal computers, radios, radiophones, stereo cassette tape players etc. Such batteries are typically available in two different types such as those characterized as rechargeable or non-rechargeable and exhibit different end of life voltage characteristics and effective series resistances. Non-rechargeable battery types are those ordinary alkaline batteries that should not be subjected to recharging attempts. Rechargeable battery types are those nickel-cadmium (Ni—Cd), nickel-hydrogen (Ni—H), lithium-ion and recently developed nickel metal-hydride (Ni—MH) batteries that should be charged at different rates with different conditions.
When a rechargeable battery is used as a power supply system for a portable personal computer, cellular phone, and the like, the battery may be charged by a battery charger in different charging modes, for example, a run and charging mode and a run or charging mode. During the run and charging mode, the battery is charged regardless of whether an end device is operating or not, and as a result, the charging operation may be difficult to control. In contrast to the run and charging mode, the run or charging mode allows the battery to be charged selectively depending upon whether the end device is operating or not.
Generally, charging operations of such a battery may be classified in at least one of a fast or rapid charging, a quick charging, a standard charging, and a trickle charging modes. The charging modes may be in relation with charging capacities or charging current of the battery. In the fast charge mode, a relatively larger charging current may be applied to the battery over a relatively short period of time, for example one to two hours. In the quick charge mode, a relatively large charging current may be applied to the battery over a relatively shorter period of time, for example four to six hours. In the standard charge mode, a relatively smaller charging current may be applied to the battery over a relatively longer period of time, for example eight to ten hours. In the trickle charge mode, the battery charging circuit provides a relatively even smaller constant current to the battery without interruption. In this mode, the battery may not be charged but its power loss due to natural discharge may be compensated.
During all charging operations, a charge level of the battery may be monitored so that, when the battery reaches its maximum charge level, the charging operation is terminated in order to prevent overcharging and damage of the battery.
Thus, it is with respect to these considerations and others that the present invention has been made.